A study on the biochemical and antigenic nature of the excretory and secretory products of Schistosoma japonicum is proposed. Extracellular substances produced by S. japonicum will be isolated and characterized by physico-chemical techniques. The role they play in the biochemistry of the parasite as well as their function in the host- parasite relationship will be studied. Following this, the relationship of these secretory and excretory products to immunopathology of schistosomiasis will be investigated.